Conventionally, various devices for conveying cards have been known in the forms of card reader/writers for reading and writing various forms of information from and into media such as IC storage cards incorporating IC storage devices and other media which can store information by optical, magnetic, electronic and other means.
According to a known device, a card inserted into a casing is interposed between a drive roller and a driven roller opposing each other, and is conveyed thereby. An upper frame of a casing carries a pair of drive rollers, and a lower frame of the casing carries a pair of driven rollers so as to define a pair of nips along a card guideway. One of the drive rollers is coupled coaxially with a drive pulley which is belt driven by a motor. Further, the two drive rollers are coupled with each other by way of coaxially arranged transmission pulleys around which a belt is passed.
According to such a structure, since the pulleys are rotatably supported around axial lines extending in parallel with the card conveying plane, the outer diameters of the pulleys are required to be reduced in order to reduce the vertical dimension of the device. However, when pulleys having smaller diameters than appropriate for the belt are used, the durability of the belt is substantially impaired. On the other hand, if pulleys having sufficiently large diameters are used, it becomes difficult to reduce the vertical dimension of the device. Furthermore, when access to the magnetic strip in the card is to be made while the card is being conveyed, it is desired to achieve a constant conveying speed, and pulleys having smaller diameters are not desirable because they produce a small flywheel effect, i.e. a small moment of inertia of the related rotating member.